The speed of semiconductor circuitry varies inversely with the resistance (R) and capacitance (C) of the interconnection system. The higher the value of the R times C product, the more limiting the circuit speed. With the continued shrinking of semiconductor devices, high resistance-capacitance (RC) delay has become a major hindrance to the further increase of the IC frequency. It has been found, however, that lowering the overall dielectric constants (κ values) of the dielectric layers employed in metal interconnects lowers the resistance capacitance (RC) of the chip and improves its performance. Thus, an essential need for low κ interlayer dielectric materials has developed. At the same time, thermal budget is of concern for the semiconductor industry leading to the requirement of low κ dielectric materials that can be processed at low temperatures. In addition, high temperature stability in excess of 400° C. of processed dielectric films is necessary to ensure circuit reliability.
Currently available low κ polymeric dielectric materials require high processing temperatures of >350° C., and are thus not best suited to meet the needs of the semiconductor industry. For example, Dow Chemical Company's SiLK™, which is an aromatic hydrocarbon polymer containing phenylene and carbonyl groups in the main chain, requires a drying step at 320° C. to remove solvent, and a final curing step at a temperature of about 400° C.
For these reasons, an essential need exists in the semiconductor industry for low-κ dielectric materials that can be fully processed at low temperatures but that remain stable at high temperatures.